Questionnaire in power plant ( 7

Questionnaire in power plant ( 7.2)

I. Fill in the blanks

1. minimum insulation resistance of components w.r.t. earth in p/p is ----------- ohms.

2. in power plant ---------- lead is earthed.

3. three modes of SMPS are --------------, -------------, --------------

4. if smoothing filter fuse fails ----------------------- .

5. Switch ON/ Switch OFF command circuits are provided in ------------------- unit.

6. The FR is protected from getting switched on, in case of any one of the phase failures by ---------------- circuit, in conventional 3 piece power plant.

7. The battery charger can deliver full rated current at --------- volts in conventional 3 piece power plant.

8. The battery charger portion of the power plant can be used as float rectifier in emergency by including ---------------- at the output.

9. The bridge rectifier elements are protected from overload by -----------------, w.r.t. conventional 3 piece power plant.

10. The output of FR is regulated within the range of -------- volts, w.r.t. conventional 3 piece power plant.

11. The overload alarm is generated by ------------ unit, w.r.t. conventional 3 piece power plant.

12. The capacity of small exchange power plant ----------- Amps.

13. The ripple should be with in ---------------- mv Psophometric without batteries.

14. Controller of Float rectifier consists --------------,------------,----------and -----------------.

15. The battery charger is prevented from switching on unless the tap changing switches are in --------,---------- and -------- positions

16. Ballast chokes are provided in the charger to limit the ------------

17. Regulation is achieved in smps by varying the --------------- in the switch

18. In FR regulation is done by ------------------, ----------------, and ------------------ methods.

19. In SCR regulation method, the SCR will be in ON condition as long as the current flowing through SCR is above threshold value called ---------- .

20. The Capacity of UPS is expressed in --------

II. True or False

1. Auto paralleling is available in small power plants.

2. Normally the float rectifier of lowest capacity available will be nominated as priority unit.

3. Output of inverter is -51 + 0.5 V DC.

4. Non priority unit (F/R) works on constant current mode.

5. Battery charger gives regulated DC output.

6. HRC fuses are provided at the DC output of the module to safe guard them against over loads in SMPS.

7. When the smoothing filter fuse fails, the FR will automatically trip.

8. In SMPS, because of low power factor, separate PF capacitors are mounted.

9. In power plants, alarm fuses are always connected in series with HRC fuses to give alarm when a HRC fuse blows.

10. the output of an SMPS power plant in float mode is 55.2 V.

11. the psophometric noise is 2 mv, when battery is floated across the output of FR.

12. Non-priority working is constant voltage mode.

13. Voltage signal -5.0 V ( w.r.t. to earth) given by a priority FR when delivering 20% of the rated load current.

14. Bypass key is associated with non priority FR.

15. Over load alarm is generated by FR

16. In smps power plants the battery is charged at constant current

17. In two piece power plants FC/BC also share the load current

18. Auto paralleling is provided in two piece power plants

19. The EMI generated by SMPS power plant is greater than the conventional

20. Rectification is done twice in SMPS power plants

21. Due to high frequency switching the size of the transformer is small in smps p/p

22. If the float voltage is high the battery will get over charged

23. If conventional batteries are floated the float voltage is maintained at 55.2V in smps

24. Provision exists to charge the conventional battery in smps

25. Drooping is provided in the FR to protect the battery

III. Answer the following Questions.

1. Draw the block diagram of battery charger and briefly explain their function.

2. Write two facilities provided in switching cubicle.

3. Write any two features of SMPS.

4. Mention 2 reasons for earthing of one pole of DC.

5. Write one or two sentences regarding following (a)Contactor (b) Contact Volt meter (c) voltage drooping (d) sequential switching (e) Ballast choke.

6. List the alarms generated in a float rectifier.

7. What are the important advantages of SMPS power plants over conventional power plants.

8. Explain the functions of switching cubicle.

9. Explain the working principle of float rectifier with a neat block schematic.

10. Write any two advantages of static rectifier compared to M.G. sets.

11. Write any four main components of a float rectifier.

12. Write components of battery charger equipment.

13. Draw the block diagram of UPS system.

14. Write any two facilities provided in FR cum BC/SC unit (SMPS).

15. Write three main characteristics of SMPS.

16. Explain output voltage droop.

17. Explain the different modes of working of smps

18. What is regulation , what are the methods employed for it

19. Write the purpose of contact voltmeter

20. How atleast one battery is kept in float, what arrangement is made to ensure it

IV. Match the following

a. Filter

b. Multi rack

c. Fine Switch

d. Rectifier

e. Charger

f. Switching cubicle

g. Inverter

1. SMPS

2. Battery Charger

3. Float Rectifier

4. Ballast choke

5. Power Transistor bridge

6. Alarm circuits

7. Smoothing circuit